The influence of gene Rv3671c in Mycobacterium bovis to its replication and acid resistance

To study the effect of Marp protein in Mycobacterium bovis to the acid resistance and growth performance, this research constructed a knockout mutant ( ΔMarp ) with mycobacteriophage, complemented strain (ΔMarpComp), and overexpressing strain (PmvRv3671) of the gene Rv3671c with pmv261 plasmid. Culturing them in standard 7H9 medium to the early logarithmic phase and transferring them into 7H9 medium at pH 6.6 and pH 5.0 and maintenance solution at pH 6.6 and pH 4.5. Likewise, macrophages Raw264.7 were infected with multiple infections at 10. The results showed that while they grew in 7H9 medium at pH 5.0 or pH 6.6 and maintenance buffer at pH 4.5, the lived number of over-expressing strain PmvRv3671 is more than wild-type strain M.bovis, ΔMarpComp and ΔMarp on the 14th day. After removing the effects of citrate solution, it can be found that the acid resistance abilities of them all are significantly lower on the 14th day than that on the 5th day. Using them infected Raw264.7 macrophages with IFNγ stimulation, the growth rate of the PmvRv3671 is better than An5, ΔMarp and ΔMarpComp. In conclusion, Rv3671c over-expressing strain had shown a better growth ability than wild-type An5, ΔMarp and ΔMarpComp under acidic environment. When exposed to pH 4.5 citrate maintenance solution for a long time, acid resistance abilities of them all have become weaker. ### Competing Interest Statement The authors have declared no competing interest.